A Floating Drag-Plate Lysimeter for Atmospheric Boundary Layer Research

Abstract

The description is presented of the design, calibration and operation of a 100-ton, floating, drag-plate, lysimeter used both for measurement of atmospheric shear stress and evapotranspiration from a growing grass turf. Calibration and operational procedures are outlined with estimates of static and measurements of dynamic errors along with typical drag-force records. Unique features of the 6 m diameter drag plate include a growing grass turf comparable to the surrounding 5-hectare field site, vectorial recording of the surface shear stress each 24 sec by means of a modern data acquisition system, and evapotranspiration measurement of the contained grass turf each 2 min on the data logging system. The drag plate has been an integral part of the atmospheric boundary layer research at Davis where flux-gradient and energy balance relationships have been studied. Preliminary findings of the momentum transfer analysis are given and previously reported results are referenced.